This invention relates to a sleeve for connecting between ferrules to hold, for example, an optical fiber.
Conventionally, split sleeves as shown in FIG. 4 have generally being used to photo-couple to one another to each other, in a simple manner, ferrules for holding an optical fiber. As shown in FIG. 4, the conventional split sleeve 100 is formed with one strip of a penetrating groove 102 in an axial direction of the cylindrical member 101, which is made of ceramics such as zirconia and usually formed by sintering a cylindrical member, then lapping an inner surface, and then forming a slit by grinding. There has also been used a split sleeve 200 as shown in FIG. 5 that has a plurality of axially-extending concave portions 202 that are spaced at such an interval as to be in parallel with each other on an inner peripheral surface 201a of the cylindrical member 201 to have one strip penetrating groove 203 formed in the axial direction.
With the shape having the one strip penetrating groove provided in the cylindrical member as shown in FIG. 4, however, the inner peripheral surface is usually formed in a surface without roughening. Accordingly, it becomes difficult to maintain the position in which the ferrule is held constant, and the inner diameter dimension tends to deviate. Therefore, there is a problem that the center of the ferrule may somewhat deviate thereby degrading alignment stability. For example, when the sleeve is used to connect ferrules holding an optical fiber, the coupling loss becomes large. Also, the split sleeve as described above tends to be affected by dusts or ground powders, raising a problem of instability in withdrawal force/coupling loss.
Under such circumstances, a split sleeve as shown in FIG. 5 has been used which has the concave portions 202 provided on the inner peripheral surface of the cylindrical member. However, the split sleeve shown in FIG. 5 has to hold a ferrule in a line so that there are disadvantages of high friction and dust occurence. Also, the contact surface between the ferrule and the cylindrical member is small so that the ferrule tends to be removed off, thus keeping the coupling state insufficient.
The present invention has been made to overcome the foregoing drawbacks in the conventional art. It is the object of the present invention to provide a sleeve which is excellent in alignment stability and capable of positively supporting a ferrule with less dust occurrence. Another object of the present invention is to provide a manufacturing method for the sleeve.